[libvirt] [PATCH v9 02/13] backup: Introduce virDomainCheckpoint APIs
Peter Krempa
pkrempa at redhat.com
Mon Jul 8 11:23:48 UTC 2019
On Sat, Jul 06, 2019 at 22:56:02 -0500, Eric Blake wrote:
> Introduce a bunch of new public APIs related to backup checkpoints.
> Checkpoints are modeled heavily after virDomainSnapshotPtr (both
> represent a point in time of the guest), although a snapshot exists
> with the intent of rolling back to that state, while a checkpoint
> exists to make it possible to create an incremental backup at a later
> time. We may have a future hypervisor that can completely manage
> checkpoints without libvirt metadata, but the first two planned
> hypervisors (qemu and test) both always use libvirt for tracking
> metadata relations between checkpoints, so for now, I've deferred
> the counterpart of virDomainSnapshotHasMetadata for a separate
> API addition at a later date if there is ever a need for it.
>
> The following map shows the API relations to snapshots, with new APIs
> on the right:
>
> Operate on a domain object to create/redefine a child:
> virDomainSnapshotCreateXML virDomainCheckpointCreateXML
>
> Operate on a child object for lifetime management:
> virDomainSnapshotDelete virDomainCheckpointDelete
> virDomainSnapshotFree virDomainCheckpointFree
> virDomainSnapshotRef virDomainCheckpointRef
>
> Operate on a child object to learn more about it:
> virDomainSnapshotGetXMLDesc virDomainCheckpointGetXMLDesc
> virDomainSnapshotGetConnect virDomainCheckpointGetConnect
> virDomainSnapshotGetDomain virDomainCheckpointGetDomain
> virDomainSnapshotGetName virDomainCheckpiontGetName
> virDomainSnapshotGetParent virDomainCheckpiontGetParent
> virDomainSnapshotHasMetadata (deferred for later)
> virDomainSnapshotIsCurrent (no counterpart, present in XML instead)
>
> Operate on a domain object to list all children:
> virDomainSnapshotNum (no counterparts, these are the old
> virDomainSnapshotListNames racy interfaces)
> virDomainSnapshotListAllSnapshots virDomainListAllCheckpoints
>
> Operate on a child object to list descendents:
> virDomainSnapshotNumChildren (no counterparts, these are the old
> virDomainSnapshotListChildrenNames racy interfaces)
> virDomainSnapshotListAllChildren virDomainCheckpointListAllChildren
>
> Operate on a domain to locate a particular child:
> virDomainSnapshotLookupByName virDomainCheckpointLookupByName
> virDomainSnapshotCurrent (obtained by flag to ListAllCheckpoints)
> virDomainHasCurrentSnapshot (no counterpart, old racy interface)
>
> Operate on a snapshot to roll back to earlier state:
> virDomainSnapshotRevert (no counterpart, instead checkpoints
> are used in incremental backups via
> XML to virDomainBackupBegin)
>
> Signed-off-by: Eric Blake <eblake at redhat.com>
> ---
> include/libvirt/libvirt-domain-checkpoint.h | 143 +++++
> include/libvirt/libvirt-domain.h | 6 +
> include/libvirt/libvirt.h | 5 +-
> src/conf/virdomainmomentobjlist.h | 5 +-
> src/driver-hypervisor.h | 38 ++
> docs/Makefile.am | 3 +
> docs/apibuild.py | 2 +
> docs/docs.html.in | 1 +
> libvirt.spec.in | 1 +
> mingw-libvirt.spec.in | 2 +
> po/POTFILES | 1 +
> src/Makefile.am | 2 +
> src/libvirt-domain-checkpoint.c | 586 ++++++++++++++++++++
> src/libvirt-domain.c | 19 +-
> src/libvirt_public.syms | 16 +
> 15 files changed, 821 insertions(+), 9 deletions(-)
> create mode 100644 include/libvirt/libvirt-domain-checkpoint.h
> create mode 100644 src/libvirt-domain-checkpoint.c
>
> diff --git a/include/libvirt/libvirt-domain-checkpoint.h b/include/libvirt/libvirt-domain-checkpoint.h
> new file mode 100644
> index 0000000000..b2d5c5758b
> --- /dev/null
> +++ b/include/libvirt/libvirt-domain-checkpoint.h
> @@ -0,0 +1,143 @@
[...]
> +typedef enum {
> + VIR_DOMAIN_CHECKPOINT_CREATE_REDEFINE = (1 << 0), /* Restore or alter
> + metadata */
> + VIR_DOMAIN_CHECKPOINT_CREATE_NO_METADATA = (1 << 1), /* Make checkpoint without
> + remembering it */
[1]
> + VIR_DOMAIN_CHECKPOINT_CREATE_QUIESCE = (1 << 2), /* use guest agent to
> + quiesce all mounted
> + file systems within
> + the domain */
> +} virDomainCheckpointCreateFlags;
[...]
> diff --git a/src/libvirt-domain-checkpoint.c b/src/libvirt-domain-checkpoint.c
> new file mode 100644
> index 0000000000..ab82d8422b
> --- /dev/null
> +++ b/src/libvirt-domain-checkpoint.c
> @@ -0,0 +1,586 @@
[...]
> +/**
> + * virDomainCheckpointCreateXML:
> + * @domain: a domain object
> + * @xmlDesc: description of the checkpoint to create
> + * @flags: bitwise-OR of supported virDomainCheckpointCreateFlags
> + *
> + * Create a new checkpoint using @xmlDesc, with a top-level
> + * <domaincheckpoint> element, on a running @domain. Note that @xmlDesc
> + * must validate against the <domaincheckpoint> XML schema.
> + *
> + * See <a href=formatcheckpoint.html#CheckpointAttributes">Checkpoint XML</a>
> + * for more details on @xmlDesc. In particular, some hypervisors may require
> + * particular disk formats, such as qcow2, in order to support this
> + * command; where @xmlDesc can be used to limit the checkpoint to a working
> + * subset of the domain's disks.
> + *
> + * If @flags includes VIR_DOMAIN_CHECKPOINT_CREATE_REDEFINE, then this
> + * is a request to reinstate checkpoint metadata that was previously
> + * captured from virDomainCheckpointGetXMLDesc() before removing that
> + * metadata, rather than creating a new checkpoint. Note that while
> + * original creation can omit a number of elements from @xmlDesc (and
> + * libvirt will supply sane defaults based on the domain state at that
> + * point in time), a redefinition must supply more elements (as the
> + * domain may have changed in the meantime, so that libvirt no longer
> + * has a way to resupply correct defaults). Not all hypervisors support
> + * this flag.
> + *
> + * If @flags includes VIR_DOMAIN_CHECKPOINT_CREATE_NO_METADATA, then
> + * the domain's disk images are modified according to @xmlDesc, but
> + * libvirt does not track any metadata (similar to immediately calling
> + * virDomainCheckpointDelete() with
[1]
> + * VIR_DOMAIN_CHECKPOINT_DELETE_METADATA_ONLY). This flag is
> + * incompatible with VIR_DOMAIN_CHECKPOINT_CREATE_REDEFINE, and is
> + * not supported by all hypervisors.
> + *
> + * If @flags includes VIR_DOMAIN_CHECKPOINT_CREATE_QUIESCE, then the
> + * libvirt will attempt to use guest agent to freeze and thaw all file
> + * systems in use within domain OS. However, if the guest agent is not
> + * present, an error is thrown. This flag is incompatible with
> + * VIR_DOMAIN_CHECKPOINT_CREATE_REDEFINE.
> + *
> + * Returns an (opaque) new virDomainCheckpointPtr on success or NULL
> + * on failure.
> + */
> +virDomainCheckpointPtr
> +virDomainCheckpointCreateXML(virDomainPtr domain,
> + const char *xmlDesc,
> + unsigned int flags)
> +{
> + virConnectPtr conn;
> +
> + VIR_DOMAIN_DEBUG(domain, "xmlDesc=%s, flags=0x%x", xmlDesc, flags);
> +
> + virResetLastError();
> +
> + virCheckDomainReturn(domain, NULL);
> + conn = domain->conn;
> +
> + virCheckNonNullArgGoto(xmlDesc, error);
> + virCheckReadOnlyGoto(conn->flags, error);
> +
> + VIR_EXCLUSIVE_FLAGS_GOTO(VIR_DOMAIN_CHECKPOINT_CREATE_REDEFINE,
> + VIR_DOMAIN_CHECKPOINT_CREATE_NO_METADATA,
> + error);
> + VIR_EXCLUSIVE_FLAGS_GOTO(VIR_DOMAIN_CHECKPOINT_CREATE_REDEFINE,
> + VIR_DOMAIN_CHECKPOINT_CREATE_QUIESCE,
> + error);
> +
> + if (conn->driver->domainCheckpointCreateXML) {
> + virDomainCheckpointPtr ret;
> + ret = conn->driver->domainCheckpointCreateXML(domain, xmlDesc, flags);
> + if (!ret)
> + goto error;
> + return ret;
> + }
> +
> + virReportUnsupportedError();
> + error:
> + virDispatchError(conn);
> + return NULL;
> +}
[...]
ACK if and only if you remove the [1] 'NO_METADATA' checkpoint creation
flag and everything related to it.
Obviously there may be some fallout from "current".
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